Computer Science Canada

Selecting objects.
Author:  metachief [ Wed May 07, 2008 10:25 pm ]
Post subject:  Selecting objects.
Hello, I am working on R.T.S. and I can't figure out how to select oneobject a a time. What I mean is: I have 3 circles on the screen and I want to have one change color by selecting it with the mouse. I want it to be something like selecting units in warcraft for examle. I'm not having trouble with the visual part. I need the concept. What variales would I have as arrays and where will I use a for loop statement? Do I need to use types for each unit?
Author:  lordroba [ Wed May 07, 2008 10:59 pm ]
Post subject:  Re: Selecting objects.
An easy way to do it would be to set up an array with records

Turing:

var cUnit : array 1 .. 100 of
    record
        x : int
        y : int
        selected : boolean
        hp : int
        %and so on...
    end record

for i : 1 .. 100
    cUnit (i).selected := false
end for


I would initially declare all units as non selected, and then when you click on a unit, (you'd figure this out by their position on the map) you'd change that unit's selected value to true. for example cUnit(23).selected:=true Then you could use if conditions with that. Say for example...

Turing:

if cUnit(i).selected=true then
%make that unit appear highlighted on screen
Author:  metachief [ Thu May 08, 2008 9:46 am ]
Post subject:  RE:Selecting objects.
Well, you din't quite answer my question, but you gave me a better way of selecting single units (I had that covered, but using records is probably better so i'll try that)

The thing that I was having troubble with was selecting multiple units at the same time. I mean highliting them. You know how in warcraft you can select many of them by clicking on the mouse and dragging it to make a square over them and if they are in that square then they are selected. Well that is what I'm trying to do.
How do I figure out weither they are in the area of the squareor not?
Author:  Tony [ Thu May 08, 2008 10:09 am ]
Post subject:  Re: RE:Selecting objects.
metachief @ Thu May 08, 2008 9:46 am wrote:
How do I figure out weither they are in the area of the squareor not?

It's much easier to figure this out if you draw a rectangle on paper then hit random dots and ask yourself "is this inside?"

And no, "well it looks like it's inside" doesn't count. Try to work out a set of math rules that make the statement definitively true. (Things like "the point is to the left of this rectangle's side" or "the point is this far away from a vertex").
Author:  lordroba [ Thu May 08, 2008 11:02 am ]
Post subject:  Re: Selecting objects.
needless to say, I was somewhat bored... Very Happy

I copied the Mouse.ButtonWait code from the help files and changed the lines to boxes.
Basically with this code, it first checks from which direction the box is drawn, and then it checks if the circles are within that box...

Turing:

var cUnit : array 1 .. 10 of
    record
        x : int
        y : int
        selected : boolean
        hp : int
        %and so on...
    end record

for i : 1 .. 10
    cUnit (i).selected := false
end for

cUnit (1).x := 110
cUnit (1).y := 110
cUnit (2).x := 120
cUnit (2).y := 20
cUnit (3).x := 30
cUnit (3).y := 130

for i : 1 .. 3
    drawoval (cUnit (i).x, cUnit (i).y, 5, 5, 9)
end for

var x, y, btnNumber, btnUpDown, buttons : int
var nx, ny : int
loop
    Mouse.ButtonWait ("down", x, y, btnNumber, btnUpDown)
    nx := x
    ny := y
    loop
        Draw.Box (x, y, nx, ny, 0)         % Erase previous line
        exit when Mouse.ButtonMoved ("up")
        Mouse.Where (nx, ny, buttons)
        for i : 1 .. 3
            drawoval (cUnit (i).x, cUnit (i).y, 5, 5, 9)
        end for
        Draw.Box (x, y, nx, ny, 1)        % Draw line to position
    end loop
    Mouse.ButtonWait ("up", nx, ny, btnNumber, btnUpDown)
    Draw.Box (x, y, nx, ny, 2)         % Draw line to final position
    for i : 1 .. 3
        if nx > x then
            if cUnit (i).x < nx and cUnit (i).x > x then
                if ny > y then
                    if cUnit (i).y < ny and cUnit (i).y > y then
                        cUnit (i).selected := true
                    else
                        cUnit (i).selected := false
                    end if
                end if
                if ny < y then
                    if cUnit (i).y > ny and cUnit (i).y < y then
                        cUnit (i).selected := true
                    else
                        cUnit (i).selected := false
                    end if
                end if
            else
                cUnit (i).selected := false
            end if
        elsif nx < x then
            if cUnit (i).x > nx and cUnit (i).x < x then
                if ny > y then
                    if cUnit (i).y < ny and cUnit (i).y > y then
                        cUnit (i).selected := true
                    else
                        cUnit (i).selected := false
                    end if
                end if
                if ny < y then
                    if cUnit (i).y > ny and cUnit (i).y < y then
                        cUnit (i).selected := true
                    else
                        cUnit (i).selected := false
                    end if
                end if
            else
                cUnit (i).selected := false
            end if
        end if
        cls
        for v : 1 .. 3
            if cUnit (v).selected = true then
                drawfilloval (cUnit (v).x, cUnit (v).y, 5, 5, 9)
            else
                drawoval (cUnit (v).x, cUnit (v).y, 5, 5, 9)
            end if
        end for
    end for
end loop


if you draw a box somewhere else, your units will be deselected
Author:  metachief [ Thu May 08, 2008 2:51 pm ]
Post subject:  RE:Selecting objects.
Cool, I never heard of Muse.ButtonWait. Althought you would probably agree that that's a lot of code just to select units. Thanks anyway, but I'm going to try to figure out a more clear and efficient way. Perhaps after experimenting with equations i'll get it. If I do I'll inform you as well.

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